1. Field of the Invention
The present invention relates to a drive train of a motor vehicle with a compressed-air system, with a compressor being provided for compressing air for the compressed-air system.
2. Description of the Related Art
Motor vehicles and compressed-air systems as relate to the present invention are known. A motor vehicle shall be understood as being any vehicle driven by way of motive power, irrespective of whether it is arranged as a road vehicle, rail vehicle, ship or other way of transport. The term compressed-air system, which is used for supplying compressed-air brakes for example, includes especially closed systems which are especially filled by way of compressed ambient air, but is not limited thereto.
In order to fill such a compressed-air system of a motor vehicle or to build up and maintain the pressure, at least one compressor is provided conventionally which is usually arranged as a reciprocating piston engine and which is driven by the drive motor of the vehicle, which is usually a combustion engine, either permanently or optionally when a respective coupling is provided.
As a result of the comparatively high pressure states in such compressed-air systems, e.g. 10 to 12.5 bar, the required drive power of the compressor is considerable and can quickly reach 5 kW or more. This power, if it needs to be provided by the combustion engine, leads on the one hand to increased fuel consumption per mileage covered by the vehicle and on the other hand to the fact that the respective power cannot be used for the drive of the motor vehicle whenever the compressor is in operation.
Document DE 30 21 691 A1 describes a drive train for a motor vehicle including: a vehicle drive engine for driving the motor vehicle via a vehicle drive shaft driven by a vehicle drive engine; and a compressor which can be driven optionally or permanently for compressing air for a compressed-air system of the motor vehicle, with the compressor being associated with at least one drive unit in the form of a steam-driven expansion machine by which the compressor can be driven.
GB 2 333 584 A discloses an exhaust-gas heat recovery system for an internal combustion engine, with the exhaust gases forming the heat source of a steam turbine which drives the piston compressor of the air-conditioning system.
DE 102 21 157 A1 describes a steam turbine which drives a compressor. The compressor compresses the aspirated ambient air to a specific final pressure.
What is needed in the art is a drive train for a motor vehicle with a compressed-air system and a compressor for compressing air for the compressed-air system, by way of which the compressor can be driven in a more energy-saving manner and at least partly without impairing the drive power of the motor vehicle. A compact embodiment which can be produced at low cost shall advantageously be created.